Aspects of the present application are related to the following non-patent literature documents, the disclosure of each of which is incorporated herein by reference in its entirety and for all purposes: “Full-Duplex Wireless Communications: Challenges, Solutions, and Future Research Directions” by Zhongshan Zhang, Keping Long, Athanasios V. Vasilakos, and Lajos Hanzo. Proceedings of the IEEE, Vol. 104, No. 7, July 2016, pp. 1369-1409; “Evaluating the Feasibility of Establishing Full-Duplex Underwater Acoustic Channels” by G. Xie, J. Gibson, and K. Bektas. In Proc. Third Annual Mediterranean Ad Hoc Networking Workshop (MedHoc), Bordrum, Turkey, June 2004; “On the Impacts and Benefits of Implementing Full-Duplex Communications Links in an Underwater Acoustic Network” by J. Gibson, A. Larraza, J. Rice, K. Smith, and G. Xie. In Proc of 5th International Mine Symposium, Naval Postgraduate School, Monterey, March 2002; “Channel Estimation and Self-Interference Cancelation in Full-Duplex Communication Systems” by Ahmed Masmoudi and Tho Le-Ngoc. IEEE Transactions on Vehicle Technology, Vol. 66, No 1, January 2017, pp. 321-334; “An Investigation Into Baseband Techniques for Single-Channel Full-Duplex Wireless Communication Systems” by Shenghong Li and Ross D. Murch. IEEE Transactions on Wireless Communications, Vol. 13, No. 9, September 2014, pp. 4794-4806; “Full-Duplex Mobile Device: Pushing the Limits” by Dani Korpi, Joose Tamminen, Matias Turunen, Timo Huusari, Yang-Seok Choi, Lauri Anttila, Shilpa Talwar, and Mikko Valkama. IEEE Communications Magazine⋅September 2016 pp. 80-87; “Full Duplex Radios” by Dinesh Bharadia, Emily McMilin and Sachin Katti. SIGCOMM′ 13, August 12-16, 2013, Hong Kong, China; and “Wave-Domain Adaptive Filtering: Acoustic Echo-Cancellation for Full Duplex Systems Based On Wave-Field Synthesis” by Herbert Buchner, Sascha Spors, and Walter Kellermann. Proceedings of ICASSP 2004 pp. iV-117-120.
It is recognized that there is an increased interest in wireless underwater communication services. An underwater acoustic communication channel may have a limited usable frequency spectrum, so spectral efficiency is a key driver in the communications research field. Due to the material properties of water in the deep sea environment, an underwater acoustical system typically requires a transmitter signal power that is many orders of magnitude greater than the required receiver signal powers (often by over 100-120 dB). This power differential arises because sound signals attenuate rapidly with distance under water. It has thus been widely held that a deep water acoustic system cannot simultaneously transmit and receive at the same frequency because a higher powered transmission signal would cause self-interference at the receiver. Such self-interference would thereby obscure the received signal by being overpowered by the transmitted signal.
The issue of self-interference has previously prevented the realization of in-band full-duplex underwater acoustic communications. At present, some acoustic communications systems have achieve full duplex operation by using uplink and downlink channels separated in time by using time-division duplexing (TDD). Alternatively, some acoustic communications systems have achieve full duplex operation by using uplink and downlink channels separated in frequency, using the frequency-division duplexing (FDD). Such TDD and FDD techniques may thereby avoid co-channel self-interference (SI).
Despite the present use of time- and/or frequency-division duplexing, full-duplex in-band systems for the underwater acoustic communications may demonstrate an obvious benefit of spectral efficiency by potentially providing twice the information capacity of the other systems. It is therefore desirable to develop a full-duplex in-band system for underwater acoustic communications to take advantage of the increased spectral efficiency available therefrom.